The present invention relates to a suction device for liquids having a motor-driven suction fan and introducing an air/liquid flow via a suction nozzle into a liquid receptacle in which the liquid is collected, and having a means for monitoring the level of liquid in the liquid receptacle in order to avoid introduction of liquid into the motor-driven suction fan, and having a display that is activated when the maximum filling level is reached.
Suction devices for liquids serve to receive cleaning liquids that have been put onto soiled floor surfaces for cleaning purposes. The liquid is sucked up by a suction air flow via a suction line having attached thereto a suction tool and is collected in the receptacle. The interior of the receptacle is in a direct flow connection with the motor-driven suction fan. In order to avoid introduction of liquid into the motor-driven suction fan the level of liquid collected in the receptacle must be monitored and must be limited to a maximum filling level.
With known suction devices a float gauge is arranged within the liquid receptacle in the flow path to the suction fan. With the rising liquid level the float gauge is moved towards the suction opening of the suction fan and when the maximum filling level is reached the opening is closed. Since no suction is observed at the suction tool and the noise level is changing due to the corresponding increase in revolving speed of the motor-driven suction fan, the operating personnel of the suction device are thus made aware that the liquid receptacle must be emptied.
In another known suction device the electric conductivity of the sucked-in dirt water between two insulated sensors is used to determine the filling level. The flowing electric measuring current is introduced into a signal processing unit and is therein processed to shut off the motor-driven suction fan and activate a display unit.
The known suction devices for liquids have the disadvantage that the surface of the liquid is exposed to the suction flow in the receptacle which results in a strong wave-like motion. Furthermore, a strong foaming of the dirt water containing detergents is observed. Both effects result in an unsatisfactory determination of the filling level due to the wave-like motion. The suction device for liquids often will shut off even though the maximum filling level has not been reached, thereby causing unnecessary operational shut-down periods.
It is therefore an object of the present invention to provide a suction device for liquids of the aforementioned kind with which an exact filling level of the dirt water in the receptacle can be determined while at the same time, the introduction of suds or liquids into the motor-driven suction fan is safely prevented.